The invention relates to an adjusting apparatus for an exhaust gas turbocharger with a valve actuated by pivotally interconnected adjustment members.
Patent application DE 10 2010 049 466 A1 discloses an adjusting apparatus for an exhaust gas turbocharger with a turbine, wherein the turbine comprises a through-flow exhaust gas guide portion and a bypass duct which serves to bypass a turbine wheel arranged in the exhaust gas guide portion. The adjusting apparatus comprises a first adjusting member and a second adjusting member. A valve element for varying the flow cross-section of the bypass duct is provided at the first adjusting member. This valve element is indirectly connected with the first adjusting member via a third adjusting member. For a specific movement of the valve element, the first adjusting member and the second adjusting member are connected so as to be movable relative to each other, with the third adjusting member being rigidly, i.e. immovably, connected with the second adjusting member. The movable connection of the first adjusting member with the second adjusting member is achieved by means of a pin-shaped connecting element, a bolt, and a locking element which secures this bolt in its position. The locking element is formed comprising the first adjusting member and the second adjusting member, so that the movable connection is made by means of a compressive stress generated by the locking element, with the first adjusting member and the second adjusting member being axially compressed by the locking element in the area of the movable connection.
During the operation of the exhaust gas turbocharger, in particular, when the exhaust gas turbocharger operates in combination with a combustion engine, the problem occurs that the exhaust gas turbocharger is subjected to temperature variations and physical vibrations.
The temperature variations are caused by continuous heating and cooling of the individual components of the exhaust gas turbocharger, with the largest temperature variations occurring in particular in the area of the turbine of the exhaust gas turbocharger due to the combustion product of the combustion engine flowing through the exhaust gas guide portion. Thus, the closer a component of the exhaust gas turbocharger is arranged at a duct through which the combustion product flows, the higher is the failure probability of this component. The repetitive temperature variations lead to a continual change in the expansion of the components, which may result in loosening, stress or material fatigue. Due to the fact that the movable connection is formed by the locking element which exerts a compressive stress on the adjusting members, one outer surface of the locking element is positioned near the duct for the combustion product and is therefore subjected to the above mentioned temperature variations.
Due to the movements of the combustion engine's components during operation, such as e.g. a reciprocating movement of the pistons, an associated rotational movement of the crank shaft or rotational movements of the cam shaft, physical vibrations may also occur. Since the exhaust gas turbocharger is mechanically connected with the combustion engine, these physical vibrations may be accompanied by disturbing noise like rattling or rustling of the adjusting apparatus of the exhaust gas turbocharger. Moreover, pulsations and vibrations of combustion gases of the combustion engine when flowing through the exhaust gas turbocharger and in particular when flowing through its bypass duct apply additional forces to the valve element and thus to the adjusting members connected with it, which even amplify these physical vibrations of the adjusting apparatus and the associated rustling and rattling noise.
In addition, these physical vibrations may also lead to loosening of originally fixed connections due to wear of relatively moving components of the connections, which ultimately may result in a reduced operational reliability, at least, however, in a limited functionality. These effects may occur, in particular, if the first adjusting member loses its nearly rectangular position in respect to a longitudinal axis of the connecting element and is inclined relative to this longitudinal axis. This inclination leads to increased physical contact forces between the relevant adjusting member and the connecting element, so that significant wear and an associated life reduction of the adjusting apparatus may occur.
It is the principal object of the present invention to provide a cost-effective adjusting apparatus for an exhaust gas turbocharger, which simultaneously increases the operational reliability and the service life due to the reduction of wear.